SEOUL (Reuters) - Shares of Korea Zinc slumped for a second straight session on Thursday, after a decision by the world's top zinc refiner to issue new stocks.

Shares fell by as much as 23.2% in Thursday's morning trade, after hitting on Wednesday their daily lower limit with a drop of 29.9%.

Korea Zinc said on Wednesday it planned to issue new stock worth about $1.8 billion, just two days after it bought back shares at a higher price, amid a battle between its co-founding families for a controlling stake.

Analysts criticised the decision as a move that could undervalue the interest of shareholders.

The country's Financial Supervisory Service is scheduled to give a briefing later on Thursday on issues related to financial markets, including the takeover battle around Korea Zinc.

Earlier this month, the market watchdog launched a probe into recent tender offers made by the two sides, urging them to refrain from any unfair practices.

Korea Zinc shares traded down 15.1% as of 0038 GMT.